Research and development have been extensively conducted on light-emitting elements using organic electroluminescence (EL) (also referred to as organic EL elements). In a basic structure of an organic EL element, a layer containing a light-emitting organic compound (also referred to as an EL layer) is provided between a pair of electrodes. By applying voltage to this element, light emission from the light-emitting organic compound can be obtained.
Since an organic EL element can be formed in the form of a film, an element with a large area can be easily formed. Thus, organic EL elements also have great potential as planar light sources which can be applied to lighting devices and the like.
For example, a lighting device including an organic EL element is disclosed in Patent Document 1.